Platelet-rich plasma - PRP Therapy

Platelet-rich plasma - PRP Therapy

Platelet-rich plasma PRP is one of the broader regenerative medicines, but shortly after its clinical application, it is not currently
the standard treatment for various orthopedic diseases. At the stage of accumulating clinical data, we ask
patients to fully understand the characteristics of this treatment method and the condition of their own disease before considering it as a treatment option.

In this "Academic Commentary Corner", we will explain the latest findings in academic societies and treatises in an easy-to-understand manner so as to help understanding and examination.


Creating PRP


PRP is made from your own blood. As you may have seen in biology textbooks, blood separates into layers as shown in the figure below when left in a test tube or centrifuged. Blood cells other than red blood cells, that is, white blood cells and platelets, gather in the central part with a volume of less than 1% and are called a buffy coat.

In reality, many platelets are suspended in the lower layer of plasma, which accounts for 55%, and this range is called Platelet Rich Plasma (PRP). PRP therapy involves extracting this part (on the right side of the figure below, surrounded by red ) with a special prp tubes and injecting it into the affected area as a treatment.

Growth factors and anti-inflammatory cytokines contained in platelets

Platelets have the role of quickly clotting blood from each other to form a clot and damming the priesthood in order to prevent blood leakage from blood vessels when bleeding occurs. However, since the publication of the research in 1970, it has become clear that it actually releases various substances to other cells and also plays a role in directing wound healing. This released substance is called "humoral factor" or "growth factor".

A "humoral factor" or "growth factor" is a small-sized protein molecule, PDGF, TGF-β, VEGF, FGF, IGF (insulin-like growth factor), HGF (hepatocyte growth factor), BMP (bone formation). Protein) etc. (* 3).

Different types of PRP

There are several types of PRP in a bite. The composition of PRP depends on the kits and test tubes used to make it. Furthermore, since self-peripheral venous blood naturally differs from person to person depending on the individual who collects blood, it is not possible to simply compare the results of the same treatment as with drugs. The major differences are shown in the table below. At this hospital, two treatment methods, LR-PRP and PFC-FD, shown in the table below are available.

Mechanism of action of PRP

Platelets release many humoral and growth factors when healing wounds (called "wound healing"). Its components include PDGF (platelet-derived growth factor), TGF-β (β-type mutant growth factor), VEGF (vascular endothelial growth factor), FGF (fibroblast growth factor), IGF (insulin-like growth factor), and HGF ( Hepatocyte growth factor), BMP (bone-forming protein), etc. are known (* 3). In basic experiments using cell culture, PRP promotes chondrocyte differentiation, proliferation, and cartilage substrate production by the action of these protein molecules. In addition, it was found that it has the effect of increasing hyaluronic acid present in the joint cavity and lubricin released from articular cartilage surface cells and synovial cells, and suppressing the expression of substrate degrading enzymes (MMP: matrix degrading enzymes, etc.). (* 5).
However, it is not clear how the effect of improving clinical symptoms such as joint pain is obtained. However, it is speculated that the above-mentioned humoral factors and growth factors released from platelets contribute to the tissue remodeling and anti-inflammatory effects during wound healing.

As introduced earlier, there are various extraction and purification methods for PRP, and the number of platelets per mL, the presence or absence of white blood cells contained, and the number of white blood cells contained differ from sample to sample. Above all, the presence or absence of leukocytes may greatly affect the action.

Leukocyte-rich PRP, which is rich in leukocytes, has a high pro-inflammatory effect, has a catabolism to the injection site (decomposes tissue structure), and contains a large amount of substrate-degrading enzymes (MMP: matrix-degrading enzymes, etc.). Is suggested (* 3). On the other hand, leukocyte-poor PRP, which does not contain a lot of white blood cells, has a high anti-inflammatory effect, has an anabolic effect on the injection site (assembles tissue structure), and suppresses substrate degrading enzymes (MMP: matrix degrading enzymes, etc.). , Is inferred.

Autologus protein solution (APS) is intended to increase the concentration of anti-inflammatory cytokines by further dehydrating LR-PRP, and its use is increasing in Japan as well. In fact, a study comparing the levels of cytokines contained in PRP has reported that IL1-ra, one of the anti-inflammatory cytokines, is abundant in APS.